Machine ringing system



Juhe 24, 1941.

- ANS.

CORD

W. E. DARROW EI'AL.

MACHINE RINGING SYSTEM 3 Sheets-Sheet 1 Filed Nov. 25, 1939 m z. mmow INVENTORS: 6./tPETE RSO/V By LAYOST ATTORNEY jun: 24, 1941. DARRQW Em 2,246,576

MACHINE RINGING SYSTEM Filed Nqv. 2 5 1959 s Sheets-Sheet? W. E. DAR/POW I INVENTORS'G. H. PETERSON L.A. rosr ATTOQNEV' June 24, 1941. w, DARROW E'TAL 2,246,576

MACHINE RINGING SYSTEM 1 I Filed Nov. 25,. 1.959 3 Sh eets-Sheet 3 M E. DARROW INVENTORS: 0.. PETERSON LA. 0 T By I S A TTORNEY Patented June 24, 1941 UNITED STATES PATENT OFFICE momma nmeme SYSTEM Wirt EQDarrow, Hiillis, N. Y., and George H. jPeterson, Glen Rock, and Lloyd A. Yost, Fanwood, N. J., asslgnors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application Noveinber 25, 1939, Serial No. 306,062

2 Claims.

This invention relates to telephonesystemsand more particularly to telephone switchboards emplaying so-called machine ringing. v A

In Patent 1,606,161 issued November 9, 1926, to CB. Fowler, a well-known machine ringing system is disclosed in which 'each cord circuit at an operator's position has associatedtherewith a plurality of relays which are controlled by means of a, common or master ringing key arrangement to connect a common ringing source to the cord to which the operator's telephone is connected and which (cord) is connected. to a called line. When a ringing key is operated, the master key circuit is connected through to the cord, which is in condition for ringing, and certain of the ring ing control relays of the cord are operated, after which the ringing key circuit is disconnected and may be used to set ringing on another cord,.and thereafter ringing current is intermittently and automatically applied to the cord and thence to the called line until the called s bscribenanswers, whereupon the cord relays are restored,

and the ringing current disconnected.

The above prior art arrangement is very satisfactory but is relatively expensive due to thefact that each cord requires the. additionofat least four extra relays in addition tothe. master ringing key equipment in order to provide the ma chine ringing service. In aswitchboard position equipped withfifteen cords it willftherefore, be

observed that about sixty eiitra relays are reaimed for the cords alone.

An object of the present invention is to provide machine ringing facilities at switchboard positions with. a substantial reduction in the cost, i. e., with relatively fewer relays per position.

A feature of the invention whereby the foregoing object is obtained resides in dividing the cords into groups, for example, into groups of five, adding one extra relay per cord and providing a common set of ringing control relays for each group, which relays are in turn controlled in the usual manner by means of a common or positional master ringing key equipment.

The invention will be understood from the following description and accompanying drawings.

The invention will be understood from the following description when read in connection with the accompanying drawings (Figs. 1, 2 and 3) arranged in accordance with Fig. 4, Fig. 1 of which represents a plurality of conventional common battery operator's cord circuits Cl, C2, etc., arranged in groups of five, the first or No. 1 cord being shown in sufficient detail for an understanding of the circuit operation of the inven- MR2, etc.

Fig. 2 shows a common ringing control circuit for each group of five cords designated as MR0! and MRC2 and Fig. 3 shows a position master ringing equipment by means of which the operator is enabled to select the proper ringing current to be connected to the called subscribers line.

A description of the operation of the circuit of this invention follows: Let us assume that the, operator has connected the front or calling plug I of cord circuit Cl tothe jack 2 of a four-party subscribers line, has operated the talking key 3 andidesires to ring the subscriber whose bell is connected between the tip conductor of the line and ground and Whose code is one ring repeated at regular intervals until the subscriber answers by removing the receiver from the switchhook, which subscriber may be designated the W. party.

In order to set the control circuit to effect this combination, the operator momentarily actuates theWringing key (Fig. 3) thereby operating relays 4 and 5 whose circuits are obvious. Relay 4 in operating .connectsbattery at its contact Iito operate relays I and 8 whose circuits can be traced from battery, contact 6 of relay 4, conductor 9, contacts III of relay II, winding of relay 1, conductor l2, contacts I 3 of key 3, winding of relay 8 and sleeve of plug I and jack 2 to ground. Relay 8. in operating, removes the short circuit from condensers l4 and It in the cord and connects the tip and ring of the front or calling end of the cord over conductors l6 and I! to the control circuit MRCI. Relay 5 operated simultaneously with relay 4 thereby operating relay H) which relay connects battery to conductor I9. When relay I operated due to the operation of relay 4, it closed its contacts 2| and 22 thereby operating relay 20 and also connected ground to conductor 23 thereby providing a locking ground for relay 5 whereupon key W can be released and used to set ringing for another cord group. Relay 1 also looks itself, and relay 8, operated under control of the talk key and the plug and jack connection. Further, relay 7 by closing its lower contacts 24 extends battery from conductor I9 to operate relay l I, the circuit for whichcan be traced from battery, contacts of relay I8, conductor l9, contacts 24 of relay 1, contacts 25 of relay 26, com

It will now be observed that relays 8, H and v 20 are operated and held under control of the sleeve circuit and contacts of the tripping relay 33 independent of either the talk key 3 or ringing key W and therefore these keys can be reof relay 44, conductors 5D and 5|, contacts 52 of relay 1 and winding of relay 31 to battery, which reverses the tip and ring conductors l6 and I1 with respect to the ringing interrupter commutator 43 whereupon ringing current and battery potential are alternately connected to the line as before but in a reverse direction.

If the J party is to be rung whose bell is connected between the ring conductor and ground and whose code is two rings, repeated at regular intervals, operation of the J key operates relay leased without interfering with the subsequent:

ringing operation. Release of thetalk key 3 and key W permit relays 1, 5, 4 and It to release.

Lamp 29 serves as an indication to the operator that control circuit MRCI is set forringing on the first group of cords (Nos. 1 to 5) and therefore as long as this lamp is lighted no other cord in this group can ring on a subscribers line.

With relays 8, 2D and Il operated, the tip of th front or calling end of the cord is connected to ground over contacts 34 of relay 8, conductor l3, contacts 35 of relay 20 and contacts'36 of relay 31 and the ring conductor of the cord is connected to the ringing interrupter RI over contacts 38 of relay 8, conductor 11, contacts 39 of relay 20, contacts 40 of relay 31, winding of tripping relay 33, contacts 4| of relay II and contacts 42 of relay 2G to the one ring per cycle commutator 43 of the ringing interrupter RI which alternately connects the circuit, just traced, to battery and the ringing generator G in a well-known manner.

When the called subscriber answers, tripping relay 33 operates, as is well understood, thereby extinguishing lamp 29 and releasing relay 20 which momentarily grounds the tip ring conductors of the lin to absorb any charge thereon due to the ringing current. Relay 2|] also releases relay H which in turn releases relay 8 thereby disconnecting the cord conductors from th position circuit.

As soon as lamp 29 is extinguished, the operator can set ringing on any other cord in the group if desired. i

In case party R is to be rung and whose code i also one ring but whose bell is connected between the tip of the line and ground, the operator will proceed as before but willactuateringing key R whereupon relay 44 instead of 5 cperates. Relays 4, 1, 8, I8, 20 and H operate as before and also reversing relay 31 operates in a circuit which can be traced from groundcontacts 2! of relay 1, conductors 23,' contacts 49 45 and relays 4, 1, 8, I8, 20 and H as before. Also relay'26 instead of relay 31 operates which con- "nects thering conductor 11 to interrupter commutator 4B which connects and disconnects generator G twice per revolution of commutator 46. Operation of ringing key M operates relays 41, 4, 1, 8, I8, 23, H and both relays 26 and 31 and thereby connects the tip conductor I6 to commutator 46 thus causing two ringing current impulses per revolution of commutator 43 to be transmitted over the tip of the line.

What is claimed is:

1. In a telephone switchboard, a called line, a plurality of cord circuits divided into groups, an operators telephone, means individual to each cord for connecting said telephone thereto, a source of ringing current and a plurality of selective keys common to said groups, ringing control means individual to each group of cords and controlled by said keys for extending said source to its respective groups of cords, and a relay individual to each cord jointly responsive to connection of said telephone thereto, connection of the cord to a line, and actuation of one of said keys for connecting said extended source through the cord to the line to the exclusion of all other cords of the group.

2. In a telephone switchboard, a called line, a plurality of cord circuits divided into groups, an operators telephone, means individual to each cord for connecting said telephone thereto, a source of ringing current, and a plurality of keys common to all of said cord circuits, ringing controlmeans individual to each group of cords and controlled by said keys for extending said source to the respective group of cords, and relay means individual to each cord, jointly responsive to actuation of the associated telephone connecting means, connection of the cord to a line, and operation of one of said keys, to connect the respective cord to, the extended source of ringing current to the exclusion of all other cords of the group.

' WIRT E. DARROW.

GEORGE E. PETERSON. LLOYD A. YOST. 

